Introduction
Water pollution from excess nitrogen and phosphorus (nutrients) is harming the environmental and economic viability of our nation’s waters. Human activities have led to a significant increase in nitrogen and phosphorus in the biosphere, altering biological communities in aquatic ecosystems, impairing drinking water, and threatening the growth of businesses and economic sectors that rely on high-quality and sustainable sources of water such as tourism, farming, fishing, manufacturing, and transportation. Recent estimates suggest that nitrogen and phosphorus pollution in freshwaters costs the U.S. at least $2.2 billion annually, with the greatest losses attributed to diminished property values and recreational uses of water (Dodds et al. 2009).

In aquatic ecosystems, nitrogen and phosphorus act as fertilizers leading to eutrophication, or an increase in the rate of supply of organic matter/plant biomass in an ecosystem. This eutrophication includes increased noxious aquatic plant growth and harmful algal blooms which result in the production of toxins that pose a threat to human, pet, and livestock health. Harmful algal blooms in U.S. coastal waters cost an additional estimated $82 million annually, with the majority of impacts in the public health and commercial fisheries sectors (Hoagland and Scatasta 2006). Eutrophication can also lead to hypoxia, or low dissolved oxygen concentrations, leading to fish kills and decreased biodiversity. Adverse impacts from nitrogen and phosphorus pollution occur in 65% of the nation’s major estuaries (Bricker et al. 2007) and there are 166 coastal hypoxic dead zones in the U.S. (Diaz and Rosenberg 2008).

As part of EPA’s ongoing efforts to work collaboratively with states and other partners to accelerate nutrient load reductions and state adoption of numeric nutrient criteria, and as outlined in a March 2011 Nutrient Framework memorandum, EPA has developed the Nutrient Indicators Dataset. This Dataset consists of a set of indicators and associated state-level data to serve as a regional compendium of information pertaining to potential or documented nitrogen and phosphorus pollution, impacts of that pollution, and states’ efforts to minimize loadings and adopt numeric criteria for nutrients into state water quality standards. Information on the data source(s) used, the data collection process, and any caveats or assumptions made which should be considered when using the data, are included on each indicator’s individual web page. Other relevant information sources can be found in the References and links to other data sources section in each indicator’s web page. The data in the Nutrient Indicators Dataset are some of the best and most current information currently available on a nationwide basis, allowing for state-by-state differentiation, and will be valuable information for states and Regions working to develop and implement Nutrient Frameworks. Regions and states could evaluate the data to identify the greatest nitrogen and phosphorus sources and impacts, and focus resources and actions accordingly.

Note that the data are not automatically updated on this website and therefore may not represent real-time information. EPA recognizes that there are numerous additional sources of information on nutrient pollution that may be available on a local or regional basis, as well as individual state efforts to reduce nutrient loadings, which may not be reflected in this Dataset. In addition, data on nitrogen and phosphorus pollution at the watershed level is available via EPA’s Nitrogen and Phosphorus Pollution Data Access Tool. Users are also encouraged to consult state websites to learn more about how states are working to minimize nutrient pollution.